Effects of Transition Metal Oxides ZrO 2 , Y 2 O 3 , and Sc 2 O 3 on Radiative Heat Transfer of Low-Reactive CaO-Al 2 O 3 -Based Mold Slag

To control heat transfer between the solidifying shell and the water-cooled mold during continuous casting, the transition metal oxides, ZrO2, Y2O3, and Sc2O3, were separately added into the developed low-reactive CaO-Al2O3-based mold slags to investigate the effect on radiation heat transfer. Two kinds of master mold slags were taken into account, one included 18 pct Al2O3 and 18 pct SiO2, and the other one included 28 pct Al2O3 and 8 pct SiO2. The slag viscosity and melting temperature were measured with rotating cylinder viscometer and hemisphere-point method, respectively. The optical parameters of the slag films having different contents of transition metal oxides were measured by Fourier transform infrared spectrometer, and an optical-process model was constructed to consider the radiation from the shell surface and hot and cold sides of the solid films to the mold plate. When ZrO2, Y2O3, and Sc2O3 contents up to 4 pct, the viscosity at 1573 K fluctuated in the range of 0.05 Pa s, the melting temperature varied within a range of 15 K, except for the case of 2 pct Sc2O3, for which the melting temperature was 27 K lower than that of the master mold slag with 8 pct SiO2 and 28 pct Al2O3. The incorporation of the three transition metal oxides up to 4 pct did not have a notable effect on the viscosity or melting temperature. The addition of ZrO2 and Y2O3 effectively decreased the radiation, whereas Sc2O3 had no direct relationship with radiation. When the ZrO2 (Y2O3) concentration was increased from 0 to 4 pct, the reduction rate of radiation transfer was 26.6 pct (13.3 pct) for the mold slag containing 18 pct Al2O3 and 18 pct SiO2. The current study provides a new direction for developing low-reactive mold slag and reducing heat transfer during continuous casting.